In hydraulic pumps which are driven by an electric motor, it has been common to provide an electric motor in one housing and the hydraulic pump in another housing with the two housings positioned in line so that the motor and pump have their own sets of bearings and shafts that are usually engaged through internal and external splines or through flexible couplings. Such an arrangement is axially long and necessitates the use of mounting brackets and alignment guides.
As shown in U.S. Pat. No. 4,729,717, an electric motor driven inline hydraulic pump comprises a common housing, a stationary shaft mounted in said housing and piston type spaced pump cylinder block subassemblies that rotate around and are mounted on the shaft. Each subassembly includes a cylinder block and a plurality of circumferentially spaced pistons. The cylinder block subassemblies are positioned such that the pistons of one subassembly extend toward the other subassembly. A common yoke plate is mounted between the two cylinder blocks and bears the two groups of piston shoes, one on each of its two bearing surfaces. Each cylinder block is driven independently of and in a direction opposite the other by an electric motor integrally mounted such that its hollow rotor houses the block and drives it. All components described above are contained in one housing and operate submerged in hydraulic fluid.
The aforementioned electric motor driven inline hydraulic pump provides an electric motor and pump embodied in the same housing and coupled directly without a rotating shaft; which utilizes a simple stationary shaft that is readily made and yet maintains an accurate support for the rotating pump components; which is relatively simple, axially compact and rugged in construction; which is less costly to manufacture; which reduces the audible noise; which results in equal and opposite radial and axial forces on the yoke plate thereby reducing its stresses and the force on the supporting pintle bearings to a negligible value; which results in smaller yoke spring and yoke control piston; which eliminates dynamic seals; which readily achieves a constant power operation without the aid of a compensator valve for this region; which automatically destrokes the yoke during starting should the pressure rise faster than the motor speed; which efficiently dissipates heat from the electric motor permitting the use of smaller and lighter motors capable of large overloads for short duration.
In the aforementioned patent application Ser. No. 07/687,173 U.S. Pat. No. 5,181,837 incorporated herein by reference, there is shown and claimed a combined electric motor and pump which has the aforementioned advantages but in addition permits the pump to be entirely submerged within the hydraulic fluid interior of the housing; which is applicable to electric motors of various types such as induction electric motors, permanent magnet motors, brushless motors; and which can be adapted to various startup and speed, rotor position, pressure and fluid temperature sensing.
In accordance with the aforementioned application, the electric motor driven inline hydraulic apparatus comprises a housing having end members closing said housing, an electric motor stator mounted in said housing, an electric motor rotor, a shaft on which the rotor is mounted is journalled in the housing and a pump is integrally formed on one or both of the end members. The shaft extends .through an opening in the end member and is connected to the rotating group of the pump. Hydraulic fluid is supplied to the interior of the electric motor housing and flows through passages in the housing to the intake of the pump integral with the end member. The end member associated with the pump is formed with an enlarged chamber adjacent the inlet of the pump which functions to reduce the flow velocity and separated the contained air from the hydraulic fluid thereby reducing the operating sound level of the pump.
Among the objectives of the present invention are to provide a combined electric motor and pump wherein a pump is integrated into one or both end members of the electric motor housing; wherein the electric motor housing and end member are constructed and arranged to stabilize and condition the flow of hydraulic fluid into the pump; and wherein the pump may comprise a piston pump, vane pump or gear pump, or combinations thereof.